Merge remote-tracking branch 'origin/release/v1.46.0' into feat/v146-ai

# Conflicts:
#	src/__tests__/baselines/source-file-lines.json

docs/api/openapi.yaml

@@ -66753,9 +66753,11 @@ components:
         - direction
         - confidence
       additionalProperties: false
-      description: A linear trend over a trailing window. The window is anchored on NOW, not on the newest reading, so a
+      description: "A linear trend over a trailing window. The window is anchored on NOW, not on the newest reading, so a
         series that stopped weeks ago reports `null` for the slope instead of describing a trend that has not been
-        observed since.
+        observed since. It is also `null` when the window's readings fall on fewer than 3 calendar days (UTC) or when
+        their first and last day lie less than half the window apart (4 days for the 7-day window, 15 for the 30-day
+        one): readings minutes apart cannot carry a slope per day."
     AnalyticsCorrelations:
       type: object
       properties: